1. Field of the Invention
The present invention relates to a sheet transport apparatus provided with a jam clearing mechanism to remove a sheet causing a transport failure such as a sheet jam from a transport path.
2. Description of the Related Art
In an image formation apparatus such as a copier and printer and an image reading apparatus provided in a scanner, facsimile or the like, provided is a sheet transport apparatus which feeds an original (sheet) to each processing section such as a printing section and reading section, and discharges the sheet processed therein. The image formation apparatus and image reading apparatus are provided on their top face with a reading platen for reading the sheet that is placed with the hands. The sheet transport apparatus is provided to be openable and closable above the platen, separates to open the top surface of the platen when a sheet is set on the platen, and is used while being closed to cover the top surface of the platen after the sheet is set.
The sheet transport apparatus is provided with a plurality of transport rollers disposed along a transport path extending from a paper feed tray to a sheet discharge tray via each processing section, and is configured to pick up sheets set on the paper feed tray on a sheet-by-sheet basis to transport to the processing section, and then, discharge the sheet processed in the processing section to the sheet discharge tray. In such a sheet transport apparatus, when a transport failure (jam) occurs at some midpoint in the transport path due to a sheet jam or the like, an open/close cover for maintenance provided in the sheet transport apparatus is opened to expose the transport path, or the sheet transport apparatus itself is separated from the image formation apparatus and image reading apparatus, and the jammed sheet is thereby removed.
Further, there is a sheet transport apparatus provided with an operating dial for jam clearing to manually feed a sheet to a position that enables the jammed sheet to be grasped and pulled out from the outside in removing the jammed sheet. As disclosed in Japanese Unexamined Patent Publication No. 2005-210184 and Japanese Unexamined Patent Publication No. 2010-41464, the operating dial for jam clearing has the configuration that a coupled transport roller always rotates by a driving mechanism provided with a transport motor.
However, in the aforementioned conventional jam clearing mechanism provided with the operating dial for jam clearing, since the rotation mechanism of the operating dial is always coupled to a particular transport roller, a load caused by rotation of the operating dial arises in normal sheet transport in which any jam does not occur. Then, such a load results in upsizing of the driving motor for driving the transport roller and increases in power consumption. Further, there is the risk of causing noise and unusual sound due to rotation of the operating dial.
Many sheet transport apparatuses provided with the conventional operating dial for jam clearing control individually driving of each of some transport rollers among a plurality of transport rollers. Therefore, for example, in the apparatus configured to drive one of two transport rollers comprised of reading roller and sheet discharge roller with a first driving motor, while driving the other roller with a second driving motor, since driving transmission mechanisms of the rollers are not coupled to each other, a plurality of operating dials is required. Further, in the apparatus using a single driving motor, it is possible to control a particular transport roller individually with an electromagnetic clutch or the like, but in a state in which driving of the electromagnetic clutch is released, since the driving transmission mechanisms are not coupled to each other, a plurality of operating dials is eventually required.
When a plurality of operating dial thus exists, such a problem sometimes occurs that breakage of the sheet and sheet jam occur more unless the plurality of operating dials is concurrently rotated in the same direction, and that the state of the jam further deteriorates. Moreover, the operating dials are manually operated, and thereby tend to cause fluctuations in rotation depending on the person who operates, and there is difficulty in operability such that jam clearing action is not performed with reliability.
Therefore, it is an object of the invention to provide a sheet transport apparatus provided with a jam clearing mechanism for enabling sheet transport to be performed smoothly in a normal state, and enabling a sheet to be removed with reliability when a sheet jam or the like occurs, while facilitating feed of the jammed sheet by single rotating operation.